January 27, 2005
Global Warming Could Be Worse Than Feared
PARIS (AFP) - Global warming may be twice as bad as expected, according to a new assessment of a commonly-used yardstick of possible carbon dioxide (CO2) pollution.
Until now, most computer models of climate change predict that if atmospheric levels of CO2 reach double of the pre-industrial age, the Earth's surface temperature will be between two and five C (3.6-9.0 F) warmer when compared with 1990 levels.
But a study published Thursday in the British science journal Nature suggests that the temperature rise could be much higher -- of between nearly two (3.6 F) and more than 11 C (19.8 F).
The research comes from a highly ambitious project in "shared computing," in which more than 90,000 people in more than 140 countries downloaded a special programme to crunch through data on their personal computer.
The screensaver software, which operates when the PC is not in use, was first pioneered by a US project, SETIAhome, which sifts through radio noise from deep space that, it is hoped, may one day contain a signal from extra-terrestrial life.
The organisers of the climateprediction.net project used the volunteers' spare commuting power to run through more than 2,000 different models on possible climate change.
Once the first batch of results was obtained, the researchers selected those models that had simulated the past climate accurately.
These best-performing models were then asked to predict how much the Earth would warm after CO2 concentrations had doubled from the pre-industrial level of 280 parts per million (ppm).
The responses ranged from 1.9 (3.4 F) to 11.5 C (20.7 F), "substantially greater" than the conventional model, they found. Most estimates clustered around 3.4 C.
By comparison, the top UN scientific authority on global warming, the Intergovernmental Panel on Climate Change (IPCC), estimated in 2001 that there would be a temperature rise of between 1.4 C (2.5 F) and 5.8 C (10.4 F) from 1990-2100.
Those figures were respectively based on CO2 scenarios that ranged from 540 to 970 ppm by the end of this century.
Current CO2 levels, as recorded in March 2004 at a Hawaii monitoring station, stood at 379 ppm. In 2000, they were 368 ppm.
The burning of oil, gas and coal, the drivers of the Industrial Revolution and the foundation of the world economy today, is releasing into the atmosphere billions of CO2 that have lain buried for millions of years.
The gas hangs in the atmosphere, trapping heat from the Sun that otherwise would radiate safely back into space.
Scientists say this unbridled pollution is bound to have an effect on the world's delicately-balanced climate system.
Their big challenge, though, is to figure out when, where and how the effects will kick in, and if the change will be gradual or if there will be a "tipping point" beyond which change will be cataclysmic.
While there are many uncertainties, recent evidence suggests that carbon pollution is worsening faster than thought and that the first signs of climate change are already visible, in the form of extreme weather events such as recurrent El-Ninos, droughts, floods and storms.
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